1. Technical Field
The present invention relates to syringes for prefilled syringe.
2. Description of the Related Art
A prefilled syringe refers to a syringe filled with a medical agent. The syringe for prefilled syringe is comprised of: a syringe barrel which includes a nozzle in its top and an opening mouth in its proximal end; and a plunger which is a pushing tool that can slide liquid tightly on the inner surface of the syringe barrel. The syringe for prefilled syringe has the structure in which the top of the nozzle is sealed with a sealant, the sealant is opened during its use, and the plunger is pushed to dispense the medical agent. Further, in order to make the inner surface of the syringe barrel liquid-tight and slidable, the diameter of a gasket attached to the top of the plunger is designed to be greater than the inner diameter of the syringe barrel and a lubricant such as a silicone oil is applied to the inner surface of the syringe barrel and the surface of the gasket.
In general, it is necessary to suck a drug solution into a syringe when an injection drug in an ampoule or a vial is administered to a patient. According to the Pharmaceutical Society of Japan, however, “promotion of efficiency of work in a clinical situation”, “prevention of a medical accident such as the mix-up or incorrect administration of a drug solution”, and “reduction in the risk of contamination with a foreign substance or bacterial contamination” can be expected by omitting this manipulation in the case of a prefilled syringe, while, for commercializing prefilled syringes, it becomes important to examine the stability of drug solutions, preservative quality by plastic containers, and the like.
Especially, there is a problem that the stability of a drug solution is deteriorated by dissolving and diffusing a lubricant used for allowing a plunger to be liquid-tight and slidable on the inner surface of a syringe barrel, in the drug solution filled in the syringe. That is, for example, when a silicone oil is used as the lubricant, the silicone oil dissolved in the drug solution in the syringe might be adsorbed in a low molecular medical agent to adversely affect the long term stability of a preparation.
Technologies for solving such problems include that in Japanese Patent No. 2005-27831-A. In Japanese Patent publication No. 2005-27831-A as described above, there is disclosed a prefilled syringe including: a syringe body including a nozzle in one end side; a plunger inserted into the syringe body from another end side; and a liquid reservoir for reserving a liquid in the syringe body and discharging the liquid from a nozzle side as described above by reducing an internal volume by a pressing force from the plunger, the prefilled syringe including a structure in which a first engagement portion is formed on the inside of the syringe body and a second engagement portion engaged with the first engagement portion in a direction of moving the plunger in the syringe body is formed in the plunger. In accordance with the prefilled syringe of Japanese Patent publication No. 2005-27831-A, contamination of foreign substances into a medical agent can be avoided since a drug solution is sealed in a drug solution reservoir (bag 50) which is formed a bag-shaped film sheet body.
Further, other technologies for avoiding contamination of foreign substances into a medical agent include that in Japanese Patent publication No. 2006-167110-A. In Japanese Patent publication No. 2006-167110-A as described above, there is disclosed a syringe in which a dispersion containing a fluorinated resin, a silicone resin, a urethane resin and fine particles is applied to an inner surface of the syringe barrel and a gasket surface to form a coating layer. In accordance with the syringe of Japanese Patent publication No. 2006-167110-A, the syringe allows the avoidance of contamination of foreign substances into an medical agent and stably has high slidability since the fluorinated-resin and the silicon resin act as components for imparting slidability and the urethane resin acts as a component for imparting flexibility.